An Experimental Study of Bio-Enzyme on Black Cotton Soil as a Highway Material

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An Experimental Study of Bio-Enzyme on Black Cotton Soil as a Highway Material

1P. Jenith

1 PG Student,

M.E-Soil Mechanics and Foundation Engineering, Raja College of Engineering and Technology, Madurai, Tamilnadu.

2Mr. C. Parthiban

2 Assistant Professor, Department of Civil Engineering,

Raja College of Engineering and Technology, Madurai, Tamilnadu.

Abstract Bio-enzyme is a natural, non-toxic, non- flammable, non-corrosive liquid enzyme formulation fermented from vegetable, fruit and sugarcane extracts that improves the engineering qualities of soil, facilitates higher soil compaction densities and increases stability. A bio-enzyme called Ecozyme is used to stabilize the expansive soil. Enzymes catalyze the reactions between the clay and the organic cat-ions and accelerate the cat-ionic exchange process to reduce adsorbed layer thickness. For other types of chemical stabilization, chemicals are mixed with soil, which is difficult to mix thoroughly, but bio-enzyme is easy to use as it can be mixed with water at optimum moisture content and then it is sprayed over soil and compacted.

In this experimental study, a step is taken to stabilize the black cotton soil for the construction of roads and buildings. In this study, strength of the Untreated black cotton soil and Enzymatic soil (Ecozyme + black cotton soil) are tested after the curing period of 0days, 7days, 14days, 21days and 28days for various Ecozyme dosages 200ml/3m3, 200ml/2.5m3, 200ml/2m3, 200ml/1.5m3. The various tests such as Preliminary test, Compaction test, Unconfined Compression Test (UCC), Soaked and Unsoaked California Bearing Ratio (CBR) test are performed for Untreated soil and Enzymatic soil and also test results are tabulated. The experimental results are shows that Bio-enzyme (Ecozyme) stabilization improves the strength of the black cotton soil up to great extent, which signifies the bearing capacity and the resistance to deformation increased in the stabilized soil.

Keywords Bio-Enzyme, Ecozyme, Black Cotton Soil, Enzymatic Soil, UCC, CBR test.

  1. INTRODUCTION

    The growth of the population has created a need for better and economical vehicular operation which requires good highways having proper geometric design, pavement condition and maintenance. Black cotton soil mostly present in the districts of Tamil nadu like Ramanathapuram, thirunelveli, Salem, Coimbatore etc. Black cotton soil is good for agriculture because it is highly fertile. But it is not suitable for the construction of roads and foundation due to its instability. Black cotton soil is highly potential for shrinkage and swelling. These negative soil performance characteristics are generally attributed to the nature and quality of the fines present in the material. When poor quality soil is available at the construction site, the best option is to modify the properties of the soil so that it meets the pavement design requirements. This has led to the development of soil stabilization techniques. Since the nature and properties of

    natural soil vary widely, a suitable stabilization technique has to be adopted for a particular situation after considering the soil properties. Soil improvement by mechanical or chemical mean is widely used. Recently Bio-Enzymes have emerged as a new chemical for stabilization. Bio-Enzymes are chemicals, organic and liquid concentrated substances which are used to improve the stability of soil of soil sub base of pavement structures. Bio-enzyme is convenient to use, safe, effective and dramatically improves road quality.

    METHODOLOGY

    Material collection

    Preliminary test for black cotton soil

    Black cotton soil

    Enzyamatic soil at various dosage 200ml/3m3, 200ml/2.5m3, 200ml/2m3,

    200ml/1.5m3

    Optimum Moisture Content and Maximum Dry Density

    Test conducted for 0,7,14,21 and 28 days

    Un confined compression

    test

    California Bearing Ratio

    Test

    RESULT AND CONCLUSION

    Figure 1. Experiments Performed on Soil

  2. LITERATURE REVIEW

    Bergmann (2000) concluded through studies that Bio-Enzymes need some clay content to strengthen the soils. It was observed that at least 2% clay is needed for successful stabilization whereas 10 to 15% clay gave very good results. Shukla et al. (2003) used Bio-Enzymes to stabilize five different types of soil ranging from low clay content to very high clay content, engineering properties and strength characteristics were determined and it was found that there is little to high improvement in physical properties. Little improvement could be due to soil constituent, which has low reactivity with Bio-Enzymes. There was improvement in CBR and unconfined compression strength of soils like silty soil to sandy soil. An increase of 65 to 252% in UCS value was observed after 4 weeks of curing. Pavement design

    thickness also reduces to 25 to 40 percent. Moreover, in case of scarcity of granular material, only stabilized surface with thin bituminous surfacing can fulfill the pavement design requirement. Shankar et al. (2009) studied the effect of different dosages of Bio-Enzymes on Lateritic soil of Dakshina Kannada (district of India), having liquid limit and Plasticity Index more than 25% and 6% respectively. Tests were conducted on lateritic soil by adding different percentages of sand as well. They concluded that there is medium improvement in physical properties of lateritic soil. Therefore it was suggested that effect of Bio-Enzyme on soil should be examined in laboratory before actual field application. Higher dosage (200ml/2m3 of soil) produced 300% increase in CBR, 450% in unconfined compressive strength and permeability was reduced by 42% after four weeks of curing. It was also observed that enzyme is not effective for cohesion less soil. Lacuoture and Gonzalez (1995) conducted a comprehensive study of the TerraZyme soil stabilizer product and its effectiveness on sub-base and sub-grade soils. The reactions of the soils treated with the enzyme was observed and recorded and compared to the untreated control samples. The variation in properties was observed over a short period only and it was found that in cohesive soils there was no major variation in properties during the early days but the soil showed improved performance progressively. Sharma (2006) has conducted laboratory studies on use of bio-enzyme stabilization of three types of soils namely clay of high plasticity (CH), clay of low plasticity (CL) and silt of low plasticity (ML). It was found that the CH soil had an increase in CBR value with reduction in saturation moisture from 40 to 21% after 4 weeks of stabilization. Also it was found that there was 100% increase in unconfined compression strength. Venkatasubramanian & Dhinakaran (2011) conducted tests on three soils with varied properties and different dosages of Bio-Enzyme. Three soils had liquid limits of 28, 30 and 46% and plasticity index of 6, 5 and 6%. Increase in unconfined compressive strength after 4 weeks of curing was reported as 246 to 404%.

  3. MATERIALS

    1. Black Cotton Soil

      The black cotton soil which was used for this experiment was collected from Kovilpatti which is located in the district of Thirunelveli, Tamilnadu.

      S.No.

      Property

      Value

      1

      Specific gravity

      2.63

      2

      Grain size distribution

      Clay(%)

      20.2

      Gravel(%)

      .0

      Sand(%)

      11.8

      Silt(%)

      68.0

      3

      Atterbergs limits

      Plastic limit(%)

      35.71

      Liquid limit(%)

      54

      Plasticity index(%)

      18.29

      4

      Maximum dry density (Kn/m3)

      14.32

      5

      Optimum moisture content(%)

      24

      6

      C.B.R(%)

      Unsoaked

      5.3

      Soaked

      1.10

      7

      Unconfined compressive strength

      (Kn/m3)

      40

      Table 1. Properties of Black Cotton Soil

    2. Eco-zyme

      Eco-zyme is a non-toxic formulation of enzyme rich materials that is manufactured through a natural fermentation process using only sugars. Eco-zyme is also blended with a biodegradable surfactant that reduces the surface tension, bringing the enzymes in closer contact with the soil materials, further promoting enzymatic reactions. When mixed with water and applied during compaction, eco-zyme acts upon the soils organic fines through a catalytic bonding process producing a strong cementation effect. The result is a durable and water-resistant mix that can be used in any climatic environment as a sub-base or as primary surface natural, organic compounds. The enzymes have been tailored to provide the lock for numerous soil materials and promote the desired alteration of their properties, causing a rapid cementation process to occur.

      Table2. Property of Eco-zyme

      S.No.

      Properties

      Value

      1

      Boiling Point

      212º F

      2

      Specific Gravity

      1.04-1.06@ 25ºC

      3

      Evaporation Rate

      Same as water

      4

      Solubility in water

      Complete

      5

      Appearance/ Odor

      Brown Liquid/ odorless

      6

      PH

      Neutral

    3. Amount of Eco-zyme

    The amount of eco-zyme varies from 200ml/3m3 to 200ml/1.5m3

    For specimen 1

    200ml for 3.0 m3 of soil = 1.43 * 3.0 *1000

    = 4290 kg of soil

    For 1 kg = 0.0466 ml of enzyme

    For specimen 2

    200ml for 2.5 m3 of soil = 1.43 * 2.5 *1000

    = 3575 kg of soil For 1 kg = 0.0559 ml of enzyme

    For specimen 3

    200ml for 2.0 m3 of soil = 1.43 * 2.0 *1000

    = 2860 kg of soil For 1 kg = 0.0699 ml of enzyme

    For specimen 4

    200ml for 1.5 m3 of soil = 1.43 * 1.5 *1000

    = 2145 kg of soil For 1 kg = 0.0932 ml of enzyme

  4. EXPERIMENTAL WORK

    1. California Bearing RatioTest(CBR)

      Black cotton soil was treated with 4 dosage of enzyme (eco-zyme) at optimum moisture content 24%.California Bearing Ratio test was conducted for different proportions of black cotton soil with eco-zyme. 4days soaked CBR values of black cotton soil with different enzyme dosages in various curing days are given below,

      Table 3. Soaked CBR test results (%)

      Soil enzyme Dosage

      Curing period

      0days

      7days

      14days

      21days

      28days

      Untreated soil

      1.10

      200ml/3m3

      1.31

      1.43

      1.72

      2.2

      4.9

      200ml/2.5m3

      1.39

      1.48

      1.81

      2.31

      5.15

      200ml/2m3

      1.44

      1..58

      1.87

      2.46

      5.36

      200ml/1.5m3

      1.49

      1.64

      1.90

      2.70

      5.5

      Figure 2. Soaked CBR test

      Table 4.Unsoaked CBR Test Results (%)

      Soil enzyme Dosage

      Curing period

      0days

      7days

      14days

      21days

      28days

      Untreated soil

      5.3

      200ml/3m3

      5.45

      6.1

      7.09

      7.8

      7.92

      200ml/2.5m3

      5.60

      6.3

      7.12

      7.82

      7.99

      200ml/2m3

      5.82

      6.7

      7.3

      7.89

      8.10

      200ml/1.5m3

      5.94

      6.9

      7.6

      8.0

      8.3

      Figure 3. Unsoaked CBR test

    2. Unconfined Compression Test

      The materials used for the tests include the Black cotton soil and eco-zyme (Bio-Enzyme). The Black cotton soil obtained from the field was tested in the laboratory for Unconfined Compressive Strength. The Unconfined Compressive Strength was evaluated by stabilization with variable dosages of enzyme(200ml/3m3, 200ml/2.5m3,200ml/2m3 and 200ml/1.5m3) for 28days (0 days,7 days,14 days,21 days,28 days) of curing. The test results have been given in table.

      Table 5. Unconfined compression test (N/cm2)

      Soil enzyme Dosage

      Curing period

      0days

      7days

      14days

      21days

      28days

      Untreated soil

      40

      200ml/3m3

      44

      45

      49

      50

      58

      200ml/2.5m3

      47

      49

      54

      57

      64

      200ml/2m3

      54

      56

      59

      66

      68

      200ml/1.5m3

      57

      58

      62

      68

      71

      Figure 4.Unconfined compression test

  5. CONCLUSION

Performance of Bio-Enzyme stabilized soil has been investigated in this work. Based on the tests conducted in the laboratory, the following conclusions were drawn:

    • Best result for unsoaked CBR value was observed with dosage 200ml per 1.5m3 the percentage increase for soil sample S1, S2, S3 and S4, 7.92%, 7.99%, 8.10% and 8.3% respectively.

    • After 28 Days of stabilization with eco-zyme dosage of 200ml per 1.5m3 the soaked CBR value for the soil Samples S1, S2, S3 and S4 was 4.9%, 5.15%, 5.36% and 5.5%.

    • With the application of eco-zyme best result for ucc values was observed with the dosage 200ml/1.55m3 of eco-zyme at curing period of 28 days.

REFERENCES

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